Investigate On The Preparation Of Epoxy Resin Composite Materials And Its Tribological Performance

The epoxy resin exhibits a series of excellent properties, such as high adhesive strength, high chemical stability, mixing performance and so on, which is widely used in aerospace materials, building adhesive, internal coating of canned food and electrical packaging materials. However, due to the poor hear-resistance and heat-conducting property, the application of epoxy has been limited greatly involved in the field of tribology. In this article, the multi-walled carbon nanotubes, polyimide fabric and ionic liquid lubricated silicon dioxide hollow spheres have been used to reinforce the matrix epoxy resin by chemical modification of dopamine, micro-areas reinforcement and self lubricating method to meet the demand of the sealing ring and sliders of petrochemical equitment. The tribological properties of epoxy resin composites are investigated in detail. The specific content and conclusions are as follows.1. The multi-walled carbon nanotubes?MWNTs? were modified by self polymerization of dopamine?DA? to make the surfaces of MWNTs connect with the polydopamine?pDop? which own the hydroxyl and amino active groups. The MWNTs reinforced epoxy?EP? composites were fabricated by surface wetting method. And on the pDop platform, the interfacial interaction between MWNTs and EP is improved significantly due to the chemical bonding. The tribological properties of EP composites were investigated in detail. The results indicates that the hardness and flexural strength of EP composites were enhanced greatly with the incorporation of DA modified MWNTs. Meanwhile, the results of thermogravimetric analysis show that DA plays an important role in improving the thermal stability property of EP composites. The friction coefficients and wear rates of EP composites reduce with the increase of DA modified MWNTs content. When the content of MWNTs is 0.7wt%, the wear rate of DA modified MWNTs/EP composite reaches the lowest value, which is 85.8% lower than that of pure EP. But the wear rate of unmodified MWNTs/EP composite reaches the lowest value when the MWNTs content is 0.5wt%, which is only 17.7% decrease compared with that of pure EP. And the MWNTs agglomeration in EP composites occurs with further increase of MWNTs content. The friction mechanisms were that DA modified MWNTs were connected with EP matrix with strong covalent bonding to form a great network structure, which make the whole composite a great integration. During the friction, the MWNTs and EP share the friction load together and the initiation and growth of cracks on the worn surfaces were restricted as well as the plastic deformation due to the improvement of thermal stability.2. The polyimide?PI? fabric/EP composites modified with different content of micro-SiO₂ hollow spheres were prepared by vacuum impregnation and high temperature laminated process. The effect of PI fabric on the tribological properties of EP composites and the effect of SiO₂ on the tribological properties of PIF/EP composites were investigated systematically. Differential scanning calorimetry?DSC? was used to study the crosslinking reaction of pure EP, PIF/EP and SiO₂ modified PIF/EP composites. The results indicate that with the incorporation of SiO₂, the micro-spheres occupy the space of movement of polymer composites, which lead to the glass transition temperature of SiO₂ modified PIF/EP composites increases. The mechanical and tribological properties of PIF/EP composites were enhanced after incorporating the SiO₂. When the SiO₂ content is 2wt%, the wear rate of SiO₂ modified PIF/EP composite reaches the lowest value, which is 71.9% lower than that of PIF/EP composite. Scanning electron microscopy?SEM? observations reveal that the skeleton network structure of fabric throughout the whole composites supported the matrix. The micro spheres fill in the interstices of fabrics interwoven structure and the gaps between layers of fabrics to form the three-dimensional reinforcement with the network structure, and avoid the short board effect. In addition, the SiO₂ micro spheres crush into tiny pieces, which can be entrapped into the scratches to recover the worn surface during the tribological tests. The debrises experience the friction to be grinded into smaller debrises, resulting in the formation of smooth film on the worn surface, which protect the matrix EP from friction directly. Based on this condition, the wear-resistance of composites can be improved significantly.3. Solid-state ionic liquid lubricated SiO₂ hollow spheres?IL- SiO₂? were prepared by vacuum impregnation under high temperature. With the melting of solid-state ionic liquid into liquid-state one, the SiO₂ hollow spheres were impregnated with the liquid-state ionic liquid under high temperature. After cooling down to the room temperature, the ionic liquid would be frozen in the SiO₂ micro spheres again. In this way, the solid-state ionic liquid can prevent the ionic liquid spilling over from the micro spheres. The effect of IL-Si O2 content, friction load and velocity on the tribological properties of EP composites has been investigated in detail, and compared with the SiO₂/EP composites. The results indicate that the friction coefficients of IL-SiO₂/EP composites decrease with the increase of IL-SiO₂ content. When the IL-SiO₂ content is 15wt%, the friction coefficient of IL-SiO₂/EP composite reaches the lowest value, which is 53.9% lower than that of pure EP. However, the lowest friction coefficient of SiO₂/EP composite is just 17.1% lower than that of pure EP. At the same time, the wear rates of IL-SiO₂/EP composites keep a stable trend as the friction load and velocity increase, which is still lower than those of SiO₂/EP composites and pure EP. The SEM analysises indicate that the solid-state IL in the SiO₂ spheres melt into the liquid-state IL own to the friction heat. The liquid-state IL spill over the spheres as the friction is processed, which has a lubrication effect between the worn surface and counterpart steel. According to this phenomenon, the friction coefficient of IL-SiO₂/EP composite decreases significantly. Moreover, the SiO₂ hollow spheres crack into smaller pieces to remedy the scraches on the worn surfaces. The lubricating film is formed with the IL and friction debrises to protect the matrix EP from friction directly. As for the SiO₂/EP composites, a lot amount of debrises are formed during the tribological process without the lubrication. The scratches, pits and debrises on the worn surfaces and counterpart steel can be seen clearly. The pits on the worn surfaces evolve into fissures, which lead to the severe damage of composites.